#include "StdAfx.h"
#include "lzssbuf.h"

lzssbuf::lzssbuf(void)
{
}

lzssbuf::~lzssbuf(void)
{
}
/**************************************************************  
        LZSS.C -- A Data Compression Program  
        (tab = 4 spaces)  
***************************************************************  
        4/6/1989 Haruhiko Okumura  
        Use, distribute, and modify this program freely.  
        Please send me your improved versions.  
                PC-VAN          SCIENCE  
                NIFTY-Serve     PAF01022  
                CompuServe      74050,1022  
**************************************************************/   
#include <STDIO.H>    
#include <STDLIB.H>    
#include <STRING.H>    
#include <CTYPE.H>    
   
#define N                4096   /* size of ring buffer */    
#define F                  18   /* upper limit for match_length */    
#define THRESHOLD       2   /* encode string into position and length    
                                                   if match_length is greater than this */   
#define NIL                     N       /* index for root of binary search trees */    
   
unsigned long int   
                textsize = 0,   /* text size counter */   
                codesize = 0,   /* code size counter */   
                printcount = 0; /* counter for reporting progress every 1K bytes */   
unsigned char   
                text_buf[N + F - 1];    /* ring buffer of size N,  
                        with extra F-1 bytes to facilitate string comparison */   
int             match_position, match_length,  /* of longest match.  These are  
                        set by the InsertNode() procedure. */   
                lson[N + 1], rson[N + 257], dad[N + 1];  /* left & right children &  
                        parents -- These constitute binary search trees. */   
FILE    *infile, *outfile;  /* input & output files */   
   
void InitTree(void)  /* initialize trees */   
{   
        int  i;   
   
        /* For i = 0 to N - 1, rson[i] and lson[i] will be the right and  
           left children of node i.  These nodes need not be initialized.  
           Also, dad[i] is the parent of node i.  These are initialized to  
           NIL (= N), which stands for 'not used.'  
           For i = 0 to 255, rson[N + i + 1] is the root of the tree  
           for strings that begin with character i.  These are initialized  
           to NIL.  Note there are 256 trees. */   
   
        for (i = N + 1; i <= N + 256; i++) rson[i] = NIL;   
        for (i = 0; i < N; i++) dad[i] = NIL;   
}   
   
void InsertNode(int r)   
        /* Inserts string of length F, text_buf[r..r+F-1], into one of the  
           trees (text_buf[r]'th tree) and returns the longest-match position  
           and length via the global variables match_position and match_length.  
           If match_length = F, then removes the old node in favor of the new  
           one, because the old one will be deleted sooner.  
           Note r plays double role, as tree node and position in buffer. */   
{   
        int  i, p, cmp;   
        unsigned char  *key;   
   
        cmp = 1;  key = &text_buf[r];  p = N + 1 + key[0];   
        rson[r] = lson[r] = NIL;  match_length = 0;   
        for ( ; ; ) {   
                if (cmp >= 0) {   
                        if (rson[p] != NIL) p = rson[p];   
                        else {  rson[p] = r;  dad[r] = p;  return;  }   
                } else {   
                        if (lson[p] != NIL) p = lson[p];   
                        else {  lson[p] = r;  dad[r] = p;  return;  }   
                }   
                for (i = 1; i < F; i++)   
                        if ((cmp = key[i] - text_buf[p + i]) != 0)  break;   
                if (i > match_length) {   
                        match_position = p;   
                        if ((match_length = i) >= F)  break;   
                }   
        }   
        dad[r] = dad[p];  lson[r] = lson[p];  rson[r] = rson[p];   
        dad[lson[p]] = r;  dad[rson[p]] = r;   
        if (rson[dad[p]] == p) rson[dad[p]] = r;   
        else                   lson[dad[p]] = r;   
        dad[p] = NIL;  /* remove p */   
}   
   
void DeleteNode(int p)  /* deletes node p from tree */   
{   
        int  q;   
   
        if (dad[p] == NIL) return;  /* not in tree */   
        if (rson[p] == NIL) q = lson[p];   
        else if (lson[p] == NIL) q = rson[p];   
        else {   
                q = lson[p];   
                if (rson[q] != NIL) {   
                        do {  q = rson[q];  } while (rson[q] != NIL);   
                        rson[dad[q]] = lson[q];  dad[lson[q]] = dad[q];   
                        lson[q] = lson[p];  dad[lson[p]] = q;   
                }   
                rson[q] = rson[p];  dad[rson[p]] = q;   
        }   
        dad[q] = dad[p];   
        if (rson[dad[p]] == p) rson[dad[p]] = q;  else lson[dad[p]] = q;   
        dad[p] = NIL;   
}   
   
void Encode(void)   
{   
        int  i, c, len, r, s, last_match_length, code_buf_ptr;   
        unsigned char  code_buf[17], mask;   
   
        InitTree();  /* initialize trees */   
        code_buf[0] = 0;  /* code_buf[1..16] saves eight units of code, and  
                code_buf[0] works as eight flags, "1" representing that the unit  
                is an unencoded letter (1 byte), "0" a position-and-length pair  
                (2 bytes).  Thus, eight units require at most 16 bytes of code. */   
        code_buf_ptr = mask = 1;   
        s = 0;  r = N - F;   
        for (i = s; i < r; i++) text_buf[i] = ' ';  /* Clear the buffer with  
                any character that will appear often. */   
        for (len = 0; len < F && (c = getc(infile)) != EOF; len++)   
                text_buf[r + len] = c;  /* Read F bytes into the last F bytes of  
                        the buffer */   
        if ((textsize = len) == 0) return;  /* text of size zero */   
        for (i = 1; i <= F; i++) InsertNode(r - i);  /* Insert the F strings,  
                each of which begins with one or more 'space' characters.  Note  
                the order in which these strings are inserted.  This way,  
                degenerate trees will be less likely to occur. */   
        InsertNode(r);  /* Finally, insert the whole string just read.  The  
                global variables match_length and match_position are set. */   
        do {   
                if (match_length > len) match_length = len;  /* match_length  
                        may be spuriously long near the end of text. */   
                if (match_length <= THRESHOLD) {   
                        match_length = 1;  /* Not long enough match.  Send one byte. */   
                        code_buf[0] |= mask;  /* 'send one byte' flag */   
                        code_buf[code_buf_ptr++] = text_buf[r];  /* Send uncoded. */   
                } else {   
                        code_buf[code_buf_ptr++] = (unsigned char) match_position;   
                        code_buf[code_buf_ptr++] = (unsigned char)   
                                (((match_position >> 4) & 0xf0)   
                          | (match_length - (THRESHOLD + 1)));  /* Send position and  
                                        length pair. Note match_length > THRESHOLD.   
                    */   
                }   
                if ((mask <<= 1) == 0) {  /* Shift mask left one bit. */   
                        for (i = 0; i < code_buf_ptr; i++)  /* Send at most 8 units of */   
                                putc(code_buf[i], outfile);     /* code together */   
                        codesize += code_buf_ptr;   
                        code_buf[0] = 0;  code_buf_ptr = mask = 1;   
                }   
                last_match_length = match_length;   
                for (i = 0; i < last_match_length &&   
                                (c = getc(infile)) != EOF; i++) {   
                        DeleteNode(s);          /* Delete old strings and */   
                        text_buf[s] = c;        /* read new bytes */   
                        if (s < F - 1) text_buf[s + N] = c;  /* If the position is  
                                near the end of buffer, extend the buffer to make  
                                string comparison easier. */   
                        s = (s + 1) & (N - 1);  r = (r + 1) & (N - 1);   
                                /* Since this is a ring buffer, increment the position  
                                   modulo N. */   
                        InsertNode(r);  /* Register the string in text_buf[r..r+F-1] */   
                }   
                if ((textsize += i) > printcount) {   
                        printf("%12ld\r", textsize);  printcount += 1024;   
                                /* Reports progress each time the textsize exceeds  
                                   multiples of 1024. */   
                }   
                while (i++ < last_match_length) {       /* After the end of text, */   
                        DeleteNode(s);                                  /* no need to read, but */   
                        s = (s + 1) & (N - 1);  r = (r + 1) & (N - 1);   
                        if (--len) InsertNode(r);               /* buffer may not be empty. */   
                }   
        } while (len > 0);      /* until length of string to be processed is zero */   
        if (code_buf_ptr > 1) {         /* Send remaining code. */   
                for (i = 0; i < code_buf_ptr; i++) putc(code_buf[i], outfile);   
                codesize += code_buf_ptr;   
        }   
        printf("In : %ld bytes\n", textsize);   /* Encoding is done. */   
        printf("Out: %ld bytes\n", codesize);   
        printf("Out/In: %.3f\n", (double)codesize / textsize);   
}   
   
void Decode(void)       /* Just the reverse of Encode(). */   
{   
        int  i, j, k, r, c;   
        unsigned int  flags;   
   
        for (i = 0; i < N - F; i++) text_buf[i] = ' ';   
        r = N - F;  flags = 0;   
        for ( ; ; )
		{   
                if (((flags >>= 1) & 256) == 0) 
				{   
                        if ((c = getc(infile)) == EOF) break;   
                        flags = c | 0xff00;             /* uses higher byte cleverly */   
                }                                                       /* to count eight */   
                if (flags & 1) 
				{   
                        if ((c = getc(infile)) == EOF) break;   
                        putc(c, outfile); 
						text_buf[r++] = c;  
						r &= (N - 1);   
                } 
				else
				{   
                        if ((i = getc(infile)) == EOF) break;   
                        if ((j = getc(infile)) == EOF) break;   
                        i |= ((j & 0xf0) << 4);  j = (j & 0x0f) + THRESHOLD;   
                        for (k = 0; k <= j; k++)
						{   
                            c = text_buf[(i + k) & (N - 1)];   
                            putc(c, outfile);  
							text_buf[r++] = c;  
							r &= (N - 1);   
                        }   
                }   
        }   
}   
   
int main(int argc, char *argv[])   
{   
        char  *s;   
   
        if (argc != 4) {   
                printf("'lzss e file1 file2' encodes file1 into file2.\n"   
                           "'lzss d file2 file1' decodes file2 into file1.\n");   
                return EXIT_FAILURE;   
        }   
        if ((s = argv[1], s[1] || strpbrk(s, "DEde") == NULL)   
         || (s = argv[2], (infile  = fopen(s, "rb")) == NULL)   
         || (s = argv[3], (outfile = fopen(s, "wb")) == NULL)) {   
                printf("??? %s\n", s);  return EXIT_FAILURE;   
        }   
        if (toupper(*argv[1]) == 'E') Encode();  else Decode();   
        fclose(infile);  fclose(outfile);   
        return EXIT_SUCCESS;   
}   
  
